Radio communication system, radio communication apparatus, and ciphering method

ABSTRACT

A radio communication apparatus includes a control unit that, if a radio access bearer (RAB) for a circuit switching domain is reconfigured between a dedicated channel (DCH) and enhanced uplink dedicated channel/High Speed Downlink Packet Access (E-DCH/HSDPA) and an RAB corresponded to RAB information exists as an established RAB and there exists no transparent mode (TM) radio bearer for a core network (CN) domain included in an information element of CN domain identity (ID), and at least one TM radio bearer is included in an information element of radio bearer (RB) information to setup, calculates a start value that is used on a new RAB.

The application is a Continuation Application of co-pending applicationU.S. patent application Ser. No. 12/734,964, filed on Jul. 19, 2010,which is a National Stage of International Application No.PCT/JP2008/073753, filed on Dec. 26, 2008, which is based on and claimspriority from Japan Patent Application No. 2007-336729, filed on Dec.27, 2007, the entire contents of which is incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to technology for making cipheringconfiguration of a circuit switched (CS) call in a radio communicationsystem.

BACKGROUND ART

A radio communication system such as shown in FIG. 1 has been proposedas a radio communication system for carrying out processing of circuitswitched calls in 3GPP (3^(rd) Generation Partnership Projects).

The radio communication system shown in FIG. 1 is of a configuration inwhich UTRAN (Universal Terrestrial Radio Access Network) 10, which is aradio access network, is connected to CN (Core Network) 40.

MSC (Mobile-services Switching Center) 50 is provided in CN 40, and RNC(Radio Network Controller) 20 and Node-B (base station apparatus) 30 areprovided in UTRAN 10. However, in some forms of UTRAN 10, the functionsof RNC 20 are taken in by Node-B 30 and RNC 20 is not provided. Node-B30 is connected to UE (User Equipment) 60, which is a radiocommunication apparatus, by way of a radio interface.

Circuit switched calls include AMR frames and AMR-WB frames that havebeen encoded by an AMR (Adaptive Multi-Rate) codec and AMR-WB (AMRWideband) codec, and these AMR frames and AMR-WB frames have until nowbeen transmitted and received on DCH (Dedicated Channels). The functionof transmitting and receiving this type of circuit switched calls by aDCH is referred to as CS voice over DCH.

As shown in FIG. 2, the architecture of this CS voice over DCH uses anUL-DPDCH (Uplink Dedicated Physical Data Channel) on uplink lines and aDL-DPDCH (Downlink Dedicated Physical Data Channel) on downlink lines.In an entity referred to as MAC (Media Access Control)-d, ciphering(encryption and decryption) is implemented in AMR frames and AMR-WBframes. A method such as disclosed in Non-Patent Document 1 is used forthe ciphering method.

Here, overall operations when establishing a radio access bearer (RAB)for a circuit switching domain (CS domain) on a DCH to realize a CSvoice over DCH in a radio communication system are described withreference to FIG. 3.

In the following explanation, the radio access bearer for a circuitswitching domain is referred to as simply a “radio access bearer.”

Explanation is presented on the assumption that messages transmitted andreceived between UE 60 and UTRAN 10 are RRC (Radio Resource Control)messages, and messages transmitted and received between UTRAN 10 and MSC50 are RANAP (Radio Access Network Application Part) messages.

As shown in 3, an RRC connection is established between UE 60 and UTRAN10 in state 1101.

In Step 1102, MSC 50 next transmits to UTRAN 10 a RAB ASSIGNMENT REQUESTmessage instructing that a radio access bearer to DCH be established.

Next, in Step 1103, UTRAN 10 secures and sets DCH resources and uses aSTART value that was previously transmitted from UE 60 to implementciphering configuration in the MAC. Here, the START value is an initialvalue used in the ciphering configuration of a circuit switched call.(For example, Non-Patent Document 2). In Step 1104, UTRAN 10 transmits aRADIO BEARER SETUP message including the information elements “RABinformation for setup” instructing radio access bearer to DCH beestablished.

In Step 1105, UE 60 performs DCH settings that establish a DCH radiobearer in accordance with the instructions of the information elements“RAB information for setup” contained in the RADIO BEARER SETUP messagethat was received. In these DCH settings, both the setting of the STARTvalue and the ciphering configuration in the MAC that uses this STARTvalue are carried out. Still further, in Step 1106, UE 60 transmits toUTRAN 10 a RADIO BEARER SETUP COMPLETE message that includes the STARTvalue that was set.

UTRAN 10 subsequently, after using the START value that was transmittedfrom UE 60 to carry out updating of ciphering configuration in the MACin Step 1107, transmits a RAB ASSIGNMENT RESPONSE message to MSC 50 inStep 1108.

Recently, however, a function referred to as “CS voice over HSPA” fortransmitting and receiving AMR frames and AMR-WB frames by HSPA (HighSpeed Packet Access) was newly proposed in 3GPP RAN2 meeting #60(Non-Patent Document 3). HSPA features higher transmission speed andhigher frequency utilization efficiency than DCH.

In this CS voice over HSPA architecture, an E-DCH (Enhanced uplink DCH)is used on uplink lines and an HSDPA (High Speed Downlink Packet Access)that uses HS-DSCH is used on downlink lines, as shown in FIG. 4. Inaddition, as the ciphering of AMR frames and AMR-WB frames, encryptionis carried out in an entity referred to as RLC UM TX (Radio Link ControlUnacknowledged Mode Transmission)” and decryption is carried out in anentity referred to as RLC UM RX (RLC UM reception).

The overall operations when establishing a radio access bearer on anE-DCH/HSDPA to realize CS voice over HSPA in a radio communicationsystem is here described with reference to FIG. 5.

As shown in FIG. 5, an RRC connection is first established between UE 60and UTRAN 10 in state 1301.

In Step 1302, MSC 50 next transmits to UTRAN 10 a RAB ASSIGNEMNT REQUESTmessage instructing the establishment of a radio access bearer on anE-DCH/HSDPA.

In Step 1303, UTRAN 10 secures and sets the E-DCH/HSDPA resources. InStep 1304, UTRAN 10 further transmits a RADIO BEARER SETUP message thatincludes the information elements “RAB information for setup”instructing the establishment of a radio access bearer on theE-DCH/HSDPA.

In Step 1305, UE 60 next carries out the E-DCH/HSDPA settings forestablishing an E-DCH/HSDPA radio bearer in accordance with the “RABinformation for setup” information element instructions contained in theRADIO BEARER SETUP message that was received. In these E-DCH/HSDPAsettings, the setting of the START value and the ciphering configurationthat use this START value are also carried out in RLC. Still further, inStep 1306, UE 60 transmits to UTRAN 10 a RADIO BEARER SETUP COMPLETEmessage including the START value that was set.

In Step 1307, UTRAN 10 then uses the START value that was transmittedfrom UE 60 to implement ciphering configuration in the RLC, and then, inStep 1308 transmits to MSC 50 a RAB ASSIGNMENT RESPONSE message.

Non-Patent Document 1: 3GPP TS 33.102 6.6.3 and 6.6.4

Non-Patent Document 2: 3GPP 25.331 57.6.0, 10.3.3.38 and 8.5.9

Non-Patent Document 3: CHANGE REQUEST 25.331 CR CR3214

SUMMARY OF THE INVENTION

As described hereinabove, a radio access bearer can be established ineach DCH or each E-DCH/HSDPA in a radio communication system.

However, even when a radio access bearer is established in anE-DCH/HSDPA, circuit switched calls cannot be transmitted and receivedon the E-DCH/HSDPA if, for example, UE 60 does not support CS voice overHSPA. As a result, in this case, the radio access bearer on an existingE-DCH/HSDPA must be released and a radio access bearer newly establishedon a DCH, i.e., the radio access bearer must be reconfigured fromE-DCH/HSDPA to DCH.

Other cases in which the radio access bearer must be reconfigured fromE-DCH/HSDPA to DCH, or from DCH to E-DCH/HSDPA include, for example, acase in which RNC 20 is switched or when UE 60 has moved.

When a radio access bearer is reconfigured between DCH and E-DCH/HSDPA,circuit switched calls must be remapped from E-DCH/HSDPA to DCH or fromDCH to E-DCH/HSDPA.

As described hereinabove, in the case of the RLC TM (RLC TransparentMode), i.e., CS voice over DCH, ciphering configuration are carried outin the MAC, and in the case of RLC UM, i.e., CS voice over HSPA,ciphering configuration are carried out in the RLC. Accordingly, whenthe radio access bearer is reconfigured between DCH and E-DCH/HSDPA,ciphering configuration must be newly implemented in the MAC or RLC.

However, the configuration of COUNT-C, which is one of the variablesused in ciphering configuration, differs depending on the RLC mode(Non-Patent Document 1). The COUNT-C ciphering configuration beforereconfiguration therefore cannot be passed over without modification tothe new ciphering configuration after reconfiguration, and aninitialization value (START value) used in the initialization of COUNT-Cis necessary.

In the reconfiguration of a radio access bearer between DCH andE-DCH/HSDPA as described above, the START value must be newly set.However, because Non-Patent Document 3 makes no suggestions regardingthe method of setting the START value when reconfiguring a radio accessbearer between a DCH and an E-DCH/HSDPA, the problem arises that theciphering executed on a circuit switched call cannot be properlyachieved.

It is therefore an object of the present invention to provide a radiocommunication system, a radio communication apparatus, and a cipheringmethod that can solve the above-described problem.

The radio communication system of the present invention is a radiocommunication system that includes a radio access network and a radiocommunication apparatus, the radio communication apparatus including acontrol unit that, when reconfiguring a radio access bearer for acircuit switching domain between a DCH and an uplink line E-DCH anddownlink line HSDPA, sets the initial value used after thereconfiguration in the encryption of the radio access bearer, andincluding a transceiver that transmits to the radio access network theinitial value that was set in the control unit and that is to be usedafter the reconfiguration.

The radio communication apparatus of the present invention includes: acontrol unit that, when reconfiguring a radio access bearer for acircuit switching domain between a DCH and an uplink line E-DCH anddownlink line HSDPA, sets the initial value to be used after thereconfiguration in the encryption of the radio access bearer; and atransceiver that transmits to the radio access network the initial valuethat was set by the control unit and that is to be used after thereconfiguration.

The ciphering method of the present invention is a ciphering methodrealized by a radio communication apparatus and includes steps of: whenreconfiguring a radio access bearer for a circuit switching domainbetween a DCH and an uplink line E-DCH and a downlink line HSDPA,setting an initial value to be used after the reconfiguration in theencryption of the radio access bearer; and transmitting to a radioaccess network the initial value that was set to be used afterreconfiguration.

By means of the present invention, when reconfiguring a radio accessbearer between a DCH on one side and an E-DCH and HSDPA on the other, aradio communication apparatus sets an initial value to be used afterreconfiguration in the encryption of the radio access bearer, andtransmits to a radio access network.

Accordingly, when reconfiguring a radio access bearer, encryption can becarried out in both the radio communication apparatus and the radioaccess network using the new initial value that was set by the radiocommunication apparatus, whereby the effect is obtained in which properciphering executed on a circuit switched call is enabled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the configuration of a radio communication system;

FIG. 2 is an explanatory view of the architecture of a CS voice overDCH;

FIG. 3 is a sequence chart for explaining an example of the overalloperations when establishing a radio access bearer on a DCH in a radiocommunication system;

FIG. 4 is an explanatory view of the architecture of CS voice over HSPA;

FIG. 5 is a sequence chart for describing an example of the overalloperations when establishing a radio access bearer on an E-DCH/HSDPA ina radio communication system;

FIG. 6 is a block diagram showing the configuration of a radiocommunication apparatus according to the first to fifth exemplaryembodiments of the present invention;

FIG. 7 is a flow chart for explaining the operations of the radiocommunication apparatus according to the first exemplary embodiment ofthe present invention;

FIG. 8 is a sequence chart for explaining an example of the overalloperations when reconfiguring a radio access bearer from a DCH to anE-DCH/HSDPA in a radio communication system;

FIG. 9 is a sequence chart for explaining n example of the overalloperations when reconfiguring a radio access bearer from an E-DCH/HSDPAto a DCH in a radio communication system;

FIG. 10 is a flow chart for explaining the operation of the radiocommunication apparatus according to the second, third, and fifthexemplary embodiments of the present invention;

FIG. 11 is a flow chart for explaining the operation of the radiocommunication apparatus according to the fourth exemplary embodiment ofthe present invention;

FIG. 12 is a sequence chart for explaining another example of theoverall operations when reconfiguring a radio access bearer from a DCHto an E-DCH/HSDPA in a radio communication system; and

FIG. 13 is a flow chart for explaining the operation of the radiocommunication apparatus according to the fifth exemplary embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Best modes for working the present invention are next described withreference to the accompanying figures.

In all of the exemplary embodiments described hereinbelow, the overallconfiguration of the radio communication system itself is the same asshown in FIG. 1.

First Exemplary Embodiment

As shown in FIG. 6, UE 60 according to the present exemplary embodimentincludes: control nit 61 that, when reconfiguring a radio access bearerbetween a DCH and an E-DCH/HSDPA, sets a new START value that is theinitial value to be used in the ciphering configuration of a circuitswitched call; and transceiver 62 that transmits to UTRAN 10 the newSTART value that was set in control unit 61.

The operations of UE 60 according to the present exemplary embodimentare next explained with reference to FIG. 7.

As shown in FIG. 7, in Step 201, when reconfiguring radio access bearerbetween a DCH and an E-DCH/HSDPA, control unit 61 first sets a new STARTvalue that is used in the ciphering configuration of a circuit switchedcall.

In Step 202, transceiver 62 then transmits to UTRAN 10 the new STARTvalue that was set in control unit 61.

Accordingly, when reconfiguring a radio access bearer in the presentexemplary embodiment, ciphering configuration can be carried out in bothUE 60 and UTRAN 10 using the new initial value that was set in UE 60,whereby the effect is obtained in which proper ciphering executed on acircuit switched call is enabled.

Second Exemplary Embodiment

UE 60 according to the present exemplary embodiment is an example inwhich the operations of the first exemplary embodiment shown in FIG. 6are more concrete, the configuration itself being the same as the firstexemplary embodiment.

Control unit 61 carries out operations of, when reconfiguring a radioaccess bearer between a DCH and an E-DCH/HSDPA, calculating the STARTvalue before releasing the existing radio bearer resources, and settingthe calculated START value as the new START value.

The operations of the present exemplary embodiment are next described.

Overall Operations of a Radio Communication System

Explanation first regards the overall operations of the radiocommunication system of the present exemplary embodiment. Because theoverall operations when establishing a radio access bearer on a DCH andon an E-DCH/HSDPA are similar to the operations shown in FIGS. 3 and 5,only the overall operations when reconfiguring a radio access bearerbetween a DCH and an E-DCH/HSDPA are described here.

The overall operations when reconfiguring a radio access bearer from aDCH to an E-DCH/HSDPA are first described with reference to FIG. 8.

It is e assumed that, as shown in FIG. 8, a radio access bearer isestablished on a DCH and a circuit switched call is mapped on the DCH inStep 301 by means of the operations shown in FIG. 3.

In this state, UTRAN 10 determines that the circuit switched call is tobe remapped from the DCH to an E-DCH/HSDPA in Step 302.

In Step 303, UTRAN 10 next secures and sets the E-DCH/HSDPA resources.In Step 304, UTRAN 10 further transmits a radio bearer setup (RADIOBEARER SETUP) message contains information elements of radio accessbearer setup information (RAB information for setup) that instructs thata radio access bearer be established on the E-DCH/HSDPA.

In Step 305, UE 60 both releases the existing DCH resources and carriesout the E-DCH/HSDPA settings that establish an E-DCH/HSDPA radio accessbearer in accordance with the instructions of the information elements“RAB information for setup” that were contained in the RADIO BEARERSETUP message that was received. In these E-DCH/HSDPA settings, thesetting of the START value and ciphering configuration in the RLC thatuse this START value are implemented in Step 306, UE 60 transmits toUTRAN 10 a RADIO BEARER SETUP COMPLETE message that includes the STARTvalue that was set.

In Step 307, UTRAN 10 then uses the START value that was transmittedfrom UE 60 to implement ciphering configuration the RLC, and then, inStep 308, transmits to MSC 50 a radio access bearer assignment response(RAB ASSIGNMENT RESPONSE) message.

The overall operations when reconfiguring the radio access bearer froman E-DCH/HSDPA to a DCH are next described with reference to FIG. 9.

As shown FIG. 9, it is here assumed that in Step 401 a radio accessbearer was established on an E-DCH/HSDPA and a circuit switched call wasmapped on the E-DCH/HSDPA by means of the operations shown in FIG. 5.

In this state, UTRAN 10 determines in Step 402 to re map the circuitswitched call from the E-DCH/HSDPA to a DCH.

In Step 403, UTRAN 10 secures and sets the DCH resources, and using aSTART value that was previously transmitted from UE 60, carries outciphering configuration in the MAC. In Step 404, UTRAN 10 furthertransmits a RADIO BEARER SETUP message that includes the informationelements “RAB information for setup” instructing the establishment of aradio access bearer on the DCH.

In Step 405, UE 60 both releases the existing E-DCH/HSDPA resources andimplements the DCH settings that establish the DCH radio bearer inaccordance with the instructions of the information elements “RABinformation for setup” that were contained in the RADIO BEARER SETUPmessage that was received. In these DCH settings, the setting of a STARTvalue and ciphering configuration in the MAC that use this START valueare implemented. In Step 406, UE 60 transmits to UTRAN 10 a RADIO BEARERSETUP COMPLETE message that contains the START value that was set.

Next, in Step 407, UTRAN 10 uses the START value that was transmittedfrom UE 60 to update the ciphering configuration in the MAC and thentransmits a RAB ASSIGNMENT RESPONSE message to MSC 50 in Step 408.

Operations of UE 60

The operations of UE 60 according to the present exemplary embodimentare next described with reference to FIG. 10. Explanation here regardsthe operations that correspond to Steps 1105, 1305, 305, and 405 ofFIGS. 3, 5, 8, and 9, respectively.

As shown FIG. 10, in Step 501, control unit 61 determines whether or nota Condition 1 is satisfied for reconfiguration of the radio accessbearer from an E-DCH/HSDPA to a DCH or for reconfiguration from a DCH toan E-DCH/HSDPA based on the “RAB information for setup” informationelements contained in the RADIO BEARER SETUP message transmitted fromUTRAN 10, and proceeds to Step 502 (the succeeding processescorresponding to Steps 305 and 405 in FIGS. 8 and 9) if Condition 1 issatisfied and to Step 507 (the succeeding processes corresponding toSteps 1105 and 1305 of FIGS. 3 and 5) if Condition 1 is not satisfied.More specifically, if for example a radio access bearer that matches RABinformation (RAB info), which is a part of the “RAB information forsetup” information elements, exists as a currently established existingradio access bearer for UE 60, the RADIO BEARER SETUP message indicatesreconfiguration and Condition 1 is determined to be satisfied.

In Step 502, control unit 61 determines whether or not Condition 2 issatisfied, this Condition 2 being that a TM radio bearer does notcurrently exist for the core network domain (CN domain) that isdesignated by the core network domain ID (CN domain identity)information element contained in the RADIO BEARER SETUP message, andmoreover, that at least one TM radio bearer is contained in a “RBinformation to setup” information element that is a part of the “RABinformation for setup” information elements; and proceeds to Step 504 toexecute new START value settings if Condition 2 is satisfied andproceeds to Step 503 if Condition 2 is not satisfied. In the presentexemplary embodiment, the circuit switching domain is the CN domaindesignated by the “CN domain identity” information element that iscontained in the RADIO BEARER SETUP message, i.e., the CN domaindesignated by the RADIO BEARER SETUP message. In addition, satisfyingCondition 2 means that the RADIO BEARER SETUP message indicates thereconfiguration from an E-DCH/HSDPA to a DCH in a state in which a radioaccess bearer, that is established for UE 60 and that is for a circuitswitching domain that is mapped to a DCH, does not exist.

In Step 503, control unit 61 determines whether Condition 3 issatisfied, this Condition 3 being that the radio bearer of at least oneof RLC-AM (RLC Acknowledged Mode) or RLC-UM (RLC Unacknowledged Mode) isincluded in “RB information to setup” information elements; and proceedsto Step 504 to execute setting of a new START value if Condition 3 issatisfied, and proceeds to Step 505 if not satisfied. SatisfyingCondition 3 means that the RADIO BEARER SETUP message indicatesreconfiguration front a DCH to an E-DCH/HSDPA.

In Step 504, control unit 61 uses variables such as COUNT-C that wereused in the ciphering configuration before reconfiguration to calculatethe START value and sets the START value that is calculated as the newSTART value. The START value that was calculated is stored in a storageunit (not shown) as the new START value. As an example of the method ofcalculating the START value, the method disclosed in Non-Patent Document2 can be used.

In Step 505, control unit 61 releases the existing radio bearerresources. More specifically, control unit 61 releases the RLC entityand PDCP (Packet Data Convergence Protocol) that were used in theexisting radio bearer, and releases the radio access bearer subflowrelating to the existing radio bearer.

In Step 506, control unit 61 then uses the START value that is stored inthe storage unit at that time to establish the radio bearer that wasinstructed by the “RAB information for setup” information elements.

The processing of Steps 507˜509 that are carried out when Condition 1 isnot satisfied in Step 501 are the same as the above-described Steps502˜504.

When reconfiguring the radio access bearer in the present exemplaryembodiment as described hereinabove, the START value is calculated andthe calculated START value is set as the new START value before existingradio bearer resources are released, and as a result, the effect isobtained in which proper ciphering executed on a circuit switched callis enabled, as in the first exemplary embodiment.

In the present exemplary embodiment, a START value is calculated beforeexisting radio bearer resources are released, whereby the effect isobtained in which a START value can be set that takes into considerationvariables such as COUNT-C that were used in ciphering configurationbefore reconfiguration.

Third Exemplary Embodiment

UE 60 according to the present exemplary embodiment is another examplein which the operations of the first exemplary embodiment shown in FIG.6 are made more specific, and the configuration itself is the same as inthe first exemplary embodiment.

In other words, in summary, when reconfiguring a radio access bearerbetween a DCH and an E-DCH/HSDPA, control unit 61 carries out theoperation of setting as the new START value a START value that waspreviously transmitted to UTRAN 10 before releasing the existing radiobearer resources.

The operations of the present exemplary embodiment are next described.The overall operations of the radio communication system of the presentexemplary embodiment are, as with the second exemplary embodiment, thesame as shown FIGS. 3, 5, 8, and 9. As a result, only the operations ofUE 60 are here described.

Operations of UE 60

The operation of UE 60 according to the present exemplary embodiment isthe same as that shown in FIG. 10 with the exception of the process ofStep 504. As a result, only the process of Step 504 is here described.

In Step 504, control unit 61 sets the START value previously transmittedto UTRAN 10 (the most recent START value held by UTRAN 10) as the newSTART value. In addition, the previously transmitted START value isstored in the storage unit (not shown) as the new START value.

When a radio access bearer is reconfigured in the present exemplaryembodiment as described hereinabove, the START value that was previouslytransmitted to UTRAN 10 is set as the new START value before theexisting radio bearer resources are released, whereby the effect isobtained in which proper ciphering executed on a circuit switched callis enabled, as in the first exemplary embodiment.

In the present exemplary embodiment, the START value that was previouslytransmitted to UTRAN 10, i.e., the START value that is held by UTRAN 10is set as the new START value, whereby both UE 60 and UTRAN 10 are ableto implement ciphering configuration using the same START value for thedata of a circuit switched call that is transmitted and received betweenUE 60 and UTRAN 10 before UTRAN 10 receives the RADIO BEARER SETUPCOMPLETE message. In other words, the effect is obtained in whichsynchronization of the ciphering configuration of a circuit switchedcall, immediately after the reconfiguration of a radio access bearer, isfacilitated.

Fourth Exemplary Embodiment

UE 60 according to the present exemplary embodiment is yet anotherexample in which the operations of the first exemplary embodiment shownin FIG. 6 are made more specific, and the configuration itself is thesame as that of the first exemplary embodiment.

In other words, in summary, when reconfiguring a radio access bearerbetween a DCH and an E-DCH/HSDPA, control unit 61 calculates the STARTvalue after releasing existing radio bearer resources and sets thecalculated START value as the new START value.

The operations of the present exemplary embodiment are next described.The overall operations of the radio communication system of the presentexemplary embodiment are, as with the second exemplary embodiment, thesame as shown in FIGS. 3, 5, 8, and 9. As a result, only the operationsof UE 60 are described here.

Operations of UE 601

The operations of UE 60 according to the present exemplary embodimentare next explained with reference to FIG. 11. The operationscorresponding to Steps 1105, 1305, 305, and 405 in FIGS. 3, 5, 8, and 9,respectively, are here explained.

As shown in FIG. 11, in Step 601, control unit 61 first determines basedon the “RAB information for setup” information elements contained in theRADIO BEARER SETUP message received from UTRAN 10 whether Condition 1for the reconfiguration of the radio access bearer from an E-DCH/HSDPAto a DCH or the reconfiguration from a DCH to an E-DCH/HSDPA issatisfied, and proceeds to Step 602 (the following processescorresponding to Steps 305 and 405 of FIG. 8 and FIG. 9, respectively)if Condition 1 is satisfied, and proceeds to Step 607 (the followingprocesses corresponding to Steps 1105 and 1305 of FIGS. 3 and 5,respectively) if Condition 1 is not satisfied. More specifically, if,for example, a radio access bearer that matches the RAB information thatis a portion of the information elements “RAB information for setup” ispresent as an existing radio access bearer that is currently establishedfor UE 60, the RADIO BEARER SETUP message indicates reconfiguration andcontrol unit 1 determines that Condition 1 is satisfied.

In Step 602, control unit 61 releases the existing radio bearerresources. More specifically, control unit 61 releases the PDCP and RLCentity that are being used in the existing radio bearer and releases thesubflow of the radio access bearer relating to the existing radiobearer.

In Step 603, control unit 61 determines whether Condition 2 is satisfiedwherein a TM radio bearer of the CN domain designated by the “CN domainidentity” information element contained in the RADIO BEARER SETUPmessage does not currently exist, and moreover, at least one TM radiobearer is contained in the “RB information to setup” information elementthat is a portion of the “RAB information for setup” informationelements; and proceeds to Step 605 for executing settings of a new STARTvalue if Condition 2 is satisfied, and proceeds to Step 604 if Condition2 is not satisfied. In the present exemplary embodiment, the circuitswitching domain is the CN domain that is identified by the “CN domainidentity” information element contained in the RADIO BEARER SETUPmessage, i.e., the CN domain identified by the RADIO BEARER SETUPmessage.

In Step 604, control unit 61 determines whether Condition 3 is satisfiedwherein at least one RLC-AM or RLC-UM radio bearer is contained in the“RB information to setup” information elements, and proceeds to Step 605for executing settings of a new START value if Condition 3 is satisfiedand proceeds to Step 606 if Condition 3 is not satisfied.

In Step 605, control unit 61 calculates a START value and sets thecalculated START value as the new START value. In addition, the STARTvalue that was calculated is stored in a storage unit (not shown) as thenew START value.

Then, in Step 606, control unit 61 uses the START value that is storedin the storage unit at that time to establish the radio bearer that isdesignated by the “RAB information for setup” information element.

The processes of Steps 607˜609 that are carried out when Condition 1 isnot satisfied in Step 601 are the same as Steps 502˜504 of FIG. 10.

When reconfiguring the radio access bearer e above-described exemplaryembodiment, a START value is calculated after the existing radio bearerresources are released and the calculated START value is set as the newSTART value, whereby, as in the first exemplary embodiment, the effectis obtained in which proper ciphering executed on a circuit switchedcall is enabled.

Fifth Exemplary Embodiment

UE 60 according to the present exemplary embodiment is yet anotherexample in which the operations of the first exemplary embodiment shownin FIG. 6 are made specific, and the configuration itself is the same asthe first exemplary embodiment.

In other words, in summary, when reconfiguring a radio access bearerbetween a DCH and an E-DCH/HSDPA, control unit 61 carries out operationsof setting a new START value before releasing the existing radio bearerresources. In addition, when setting the new START value, control unit61 implements the settings of the START value by either of the methodsof the above-described second or third exemplary embodiments dependingon whether a predetermined condition is satisfied or not.

The operations of the present exemplary embodiment are next described.

Overall Operations of the Radio Communication System

The overall operations of the radio communication system of the presentexemplary embodiment are first described. The overall operations of theradio communication system, as with the second exemplary embodiment, arethe same as shown in FIGS. 3, 5, 8, and 9. However, when reconfiguring aradio access bearer from a DCH to an E-DCH/HSDPA, the operations differfrom the overall operations (FIG. 8) of the second exemplary embodimentregarding the point of setting the START value by the method of thethird exemplary embodiment. As a result, only these overall operationsare here described with reference to FIG. 12.

It is here assumed that in Step 701 the radio access bearer isestablished on a DCH by the operations shown in FIG. 3 and a circuitswitched call is mapped on the DCH, as shown in FIG. 12.

In this state, in Step 702, UTRAN 10 determines that the circuitswitched call is to be remapped from the DCH to an E-DCH/HSDPA.

In Step 703, UTRAN 10 next secures and sets the E-DCH/HSDPA resourcesand uses the START value that was previously transmitted from UE 60 tomake ciphering configuration in the RLC. In Step 704, UTRAN 10 furthertransmits a RADIO BEARER SETUP message containing the informationelement “RAB information for setup” instructing that a radio accessbearer be established on an E-DCH/HSDPA.

Next, in Step 705, in accordance with the instructions of theinformation element “RAB information for setup” contained in the RADIOBEARER SETUP message that was received, UE 60 both releases the existingDCH resources and carries out E-DCH/HSDPA settings that establish theE-DCH/HSDPA radio access bearer. These E-DCH/HSDPA settings includesetting of the previous START value to the new START value and theciphering configuration in the RLC that uses this START value. In Step706, FE 60 next transmits to UTRAN 10 a RADIO BEARER SETUP COMPLETEmessage that contains the START value that was set.

In Step 707, UTRAN 10 next uses the START value transmitted from UE 60to update the ciphering configuration in the RLC if necessary. In otherwords, if the START value transmitted from UE 60 is the same as theprevious START value, updating of the ciphering configuration is notabsolutely necessary.

In Step 708, UTRAN 10 transmits to MSC 50 a RAB ASSIGNMENT RESPONSEmessage.

Operations of UE 60

The operations of UE 60 according to the present exemplary embodimentare next described with reference to FIG. 13. The Operations of UE 60according to the present exemplary embodiment differ from the embodimentshown in FIG. 10 in that Step 504 has been changed to Steps 801 and 802and are otherwise the same. As a result, only the processes of Steps 801and 802 are here described.

As shown in FIG. 13, Step 801 is carried out when Condition 2 issatisfied in Step 502. In this Step 801, control unit 61 calculates aSTART value and sets the calculated START value to the new START value.In addition, the calculated START value is stored in the storage unit(not shown) as the new START value.

In addition, Step 802 is carried out when Condition 3 is satisfied inStep 503. In this Step 802, control unit 61 sets the START value thatwas previously transmitted to UTRAN 10 to the new START value. Inaddition, the START value that was previously transmitted is stored inthe storage unit (not shown) as the new START value.

When reconfiguring a radio access bearer in the present exemplaryembodiment as described hereinabove, the START value that was previouslytransmitted to UTRAN 10 is set as the new START value before releasingexisting radio bearer resources, whereby the effect is obtained in whichproper ciphering executed on circuit switched calls is enabled, as inthe first exemplary embodiment.

In addition, in the present exemplary embodiment, the effect is furtherobtained in which alteration of the method of setting a START valueaccording to the content of the information element “RAB information forsetup” is enabled.

For example, when the method of setting the START value previouslytransmitted to UTRAN 10 as the new START value is adopted, the effect isobtained in which the achievement of synchronization of the cipheringconfiguration of circuit switched calls by both UE 60 and UTRAN 10,immediately after the reconfiguration of the radio access bearer, as inthe third exemplary embodiment, is facilitated; and when the method ofsetting the calculated START value as the new START value is adopted,the effect is obtained in which setting of a START value that takes intoconsideration variables such as COUNT-C of the existing radio accessbearer, as in the second embodiment, is enabled.

Although the invention of the present application has been describedwith reference to exemplary embodiments, the invention of the presentapplication is not limited to the above-described exemplary embodiments.The configuration and details of the invention of the presentapplication are open to various modifications within the scope of theinvention of the present application that will be readily understood byanyone of ordinary skill in the art.

For example, although a 3GPP radio communication system was described asone example in the first to fifth exemplary embodiments, the radiocommunication system, radio communication apparatus, and cipheringmethod of the first to fifth exemplary embodiments can also be appliedin other radio communication systems in which the radio access bearer ofthe circuit switching domain is reconfigured between communicationchannels having different ciphering configuration methods (for example,variables). In such cases, ciphering configuration can be implementedusing a new initial value that is set in the radio communicationapparatus in both the radio communication apparatus and radio accessnetwork, whereby the effect is obtained in which proper cipheringexecuted on circuit switched calls is enabled.

In addition, although operations for setting a new START value beforereleasing existing radio bearer resources were described as one examplein the third and fifth exemplary embodiments, a new START value can beset after releasing the existing radio bearer resources as in the fourthexemplary embodiment.

The present application claims priority based on JP-A-2007-336729 forwhich application was submitted on Dec. 27, 2007 and incorporates all ofthe disclosures of that application.

1-23. (canceled)
 24. A radio communication apparatus, comprising: acontroller configured to, if a radio access bearer (RAB) corresponded toRAB information exists as an established RAB and there exists notransparent mode (TM) radio bearer for a core network (CN) domainincluded in an information element of CN domain identity (ID), and atleast one TM radio bearer is included in an information element of radiobearer (RB) information to setup, calculate a start value that is usedon a new RAB and release PDCP (Packet Data Convergence Protocol) and RLCentities for a radio bearer relating to the established RAB and releasethe RAB subflow associated with the radio bearer; and a transceiverconfigured to communicate with a radio access network.
 25. The radiocommunication apparatus according to claim 24, wherein the transceivertransmits the start value to a radio access network.
 26. The radiocommunication apparatus according to claim 24, information element of RBinformation to setup are included in a radio bearer setup messagereceived from a radio access network.
 27. The radio communicationapparatus according to claim 24, the start value is used forinitializing information relating with COUNT-C that is used forciphering.
 28. A radio communication method, comprising: controlling to,if a radio access bearer (RAB) corresponded to RAB information exists asan established RAB and there exists no transparent mode (TM) radiobearer for a core network (CN) domain included in an information elementof CN domain identity (ID), and at least one TM radio bearer is includedin an information element of radio bearer (RB) information to setup,calculate a start value that is used on a new RAB and release PDCP(Packet Data Convergence Protocol) and RLC entities for a radio bearerrelating to the established RAB and release the RAB subflow associatedwith the radio bearer; and a transceiver to communicate with a radioaccess network.
 29. The radio communication method according to claim28, wherein the transceiver transmits the start value to a radio accessnetwork.
 30. The radio communication method according to claim 28,information element of RB information to setup are included in a radiobearer setup message received from a radio access network.
 31. The radiocommunication method according to claim 28, the start value is used forinitializing information relating with COUNT-C that is used forciphering.